A parallel optical communications module is a module having multiple transmit (TX) channels, multiple receive (RX) channels, or both. A parallel optical transceiver module is an optical communications module that has multiple TX channels and multiple RX channels in TX and RX portions, respectively, of the transceiver module. The TX portion comprises components for transmitting data in the form of modulated optical signals over multiple optical waveguides, which are typically optical fibers. The TX portion includes a laser driver circuit and a plurality of laser diodes. The laser driver circuit outputs electrical signals to the laser diodes to modulate them. When the laser diodes are modulated, they output optical signals that have power levels corresponding to logic 1s and logic 0s. An optics system of the transceiver module focuses the optical signals produced by the laser diodes into the ends of respective transmit optical fibers held within a connector that mates with the transceiver module.
Typically, the TX portion also includes a plurality of monitor photodiodes that monitor the output power levels of the respective laser diodes and produce respective electrical feedback signals that are fed back to the transceiver controller. The transceiver controller processes the feedback signal to obtain respective average output power levels for the respective laser diodes. The transceiver controller outputs control signals to the laser driver circuit that cause it to adjust the modulation and/or bias current signals output to the respective laser diodes such that the average output power levels of the laser diodes are maintained at relatively constant levels.
The RX portion includes a plurality of receive photodiodes that receive incoming optical signals output from the ends of respective receive optical fibers held in the connector. The optics system of the transceiver module focuses the light that is output from the ends of the receive optical fibers onto the respective receive photodiodes. The receive photodiodes convert the incoming optical signals into electrical analog signals. An electrical detection circuit, such as a transimpedance amplifier (TIA), receives the electrical signals produced by the receive photodiodes and outputs corresponding amplified electrical signals, which are processed in the RX portion to recover the data.
There is an ever-increasing demand in the optical communications industry for parallel optical communications systems that are capable of simultaneously transmitting and receiving ever-increasing amounts of data. To accomplish this, it is known to combine multiple parallel optical transceiver modules of the type described above to produce a parallel optical communications system that has a higher bandwidth than the individual parallel optical transceiver modules. A variety of parallel optical transceiver modules are used in such systems for this purpose.
FIG. 1 illustrates a perspective view of an electrical connector 2, known in the industry as a Meg-Array connector, mounted on a printed circuit board (PCB) 3. The Meg-array connector 2 comprises a socket 4 having an array of electrically-conductive ball contacts (not shown) on its bottom surface and an array of electrically conductive bladed pairs 5 on its upper surface. FIG. 2 illustrates a perspective view of the Meg-array connector 2 shown in FIG. 1 after a parallel optical transceiver module 6, known in the industry as a Snap-12 parallel optical transceiver module, has been plugged into the socket 4. The snap-12 module 6 has an array of electrical contacts (not shown) on its lower surface that come into contact with respective electrically-conductive bladed pairs 5 of the Meg-Array connector 2 when the module 6 is pressed down in the Y-direction of an X, Y, Z Cartesian coordinate system into the socket 4.
A receptacle 7 is disposed within an opening formed in a front panel 8 of a box (not shown) for receiving an optical connector module (not shown). The optical connector module (not shown) is mated with the receptacle 7 by inserting the optical connector module in the Z-direction through the opening formed in the front panel 8 into the receptacle 7 such that mating features (not shown) on the inside of the receptacle 7 engage respective mating features (not shown) on the optical connector module (not shown). This type of mounting arrangement is known in the industry as an edge-mounted arrangement due to the fact that the front panel 8 constitutes an edge of the box in which the parallel optical transceiver modules are mounted. The optical connector module is mechanically and optically coupled to an end of an optical fiber ribbon cable (not shown) having a plurality (e.g., 4, 8, 12, 24, or 48) of optical fibers.
By mounting multiple of the optical transceiver modules 6 side-by-side on the motherboard PCB 3, an optical communications system with very high bandwidth can be achieved. There are, however, disadvantages associated with edge-mounted arrangements of the type shown in FIG. 2. One such disadvantage is that the receptacles 7 and the respective optical connector modules (not shown) are relatively wide in the X-dimension and therefore consume large amounts of space on the front panel 8. Because space on the front panel 8 is limited, the ability to increase bandwidth by increasing the size of the array is also limited.
Another disadvantage associated with the edge-mounted arrangement shown in FIG. 2 is that the parallel optical transceiver modules 6 are not Z-pluggable, i.e., they cannot be plugged into and unplugged from the front panel 8. Rather, before the top of the box has been secured in position, the modules 6 are plugged into their respective Meg-Array sockets 4 by placing the modules 6 over the respective sockets 4 and applying a force in the downward Y-direction. The top of the box is then secured in position. This makes the tasks of installing the modules 6 and swapping the modules 6 out relatively difficult and time-consuming.